1. Field of the Invention
The present invention relates to a toner, and more particularly, to a toner used for a non-contact heating fixation method.
2. Discussion of the Background
Fixing methods of powder toner used in an electrophotographic process include:
(1) an unheated fixing method using a pressure or a solvent;
(2) a non-contact heating fixation method that does not directly heat a toner image, such as an oven fixing method of feeding a heated air to a toner image bearer and a radiation fixing method of feeding a heat with light; and
(3) a contact heating fixation method of feeding a heat and a pressure to a toner image at the same time with a heating roller.
Many copiers and printers using an electrophotographic process use the contact heating fixation method (3), typified by the heating roller fixing method in terms of heat efficiency. However, the heating roller fixing method is not suitable for producing a high-resolution image formed of dots because the toner layer is crushed when pressed upon application of heat. Also, the method is not suitable for fixing toner images on both sides of a receiving material at the same time.
Therefore, the non-contact heating fixation method (2) is mostly used in duplex printing or copying, or copying that produces high quality images at a high speed. However, the non-contact heating fixation method (2) does not press a toner image as the heating roller fixing method does, and has less fixability than the heating roller fixing method. This phenomenon occurs when the fixing temperature is decreased to produce a low gloss image. In addition, when used in an image forming method producing multi-colored images by combining two or more toner layers having different colors, the phenomenon is very noticeable, which is a serious problem. In addition, a serious problem also occurs in color reproducibility.
Japanese Laid-Open Patent Publications Nos. 6-282102, 9-190013, 10-39539, 2000-39794, 2001-100456 and 2001-100459, etc., disclose toners preferably used for the non-contact fixing method (2). However, fixability and color reproducibility of the toners are still unsatisfactory.
Japanese Laid-Open Patent Publication No. 6-282102 discloses a melted viscosity and fixability of a rheometer. However, the printing speed is low as 5 cm/sec (50 mm/sec) and the fixing temperature is 125xc2x0 C., which is higher than that of the present invention as described below. In addition, the method of Laid-Open Patent Publication No. 6-282102 is still unsatisfactory in low gloss (low fixing temperature) printing and/or copying, high-speed printing and/or copying, duplex or combination of plural-color printing and/or copying.
Japanese Laid-Open Patent Publication No. 10-39539 discloses a rheometer, coverage of an additive and a gloss, although not disclosing fixability. This is also unsatisfactory in a field of an object of the present invention, as the above-described Japanese Laid-Open Patent Publication No. 6-282102 is. The conventional technologies disclosed in other publications are also unsatisfactory in a field of an object of the present invention, as Japanese Laid-Open Patent Publication No. 6-282102 is.
Because of these reasons, a need exists for a toner having good fixability even when used in an image forming method using a non-contact fixing method.
Accordingly, an object of the present invention is to provide a toner having good fixability, even in an image forming method using a non-contact fixing method.
Another object of the present invention is to provide a toner having good fixability without filming, even in an image forming method using a non-contact fixing method.
Yet another object of the present invention is to provide a toner having good fixability and color reproducibility, even in an image forming method of reproducing multi-colored images by combining two or more toner layers having different colors.
A further object of the present invention is to provide a toner having good heat resistance without impairing fixability and color reproducibility.
A still further object of the present invention is to provide a toner producing high quality images without impairing fixability and color reproducibility.
In addition, another object of the present invention is to provide an image forming method and an image forming apparatus using the toner, and a container containing the toner.
These and other objects of the present invention will become more readily apparent, and can be attained by a toner having a half melting temperature not greater than 115xc2x0 C. when measured by a flow tester.
In addition, the toner preferably has a half melting temperature of from 90 to 115xc2x0 C. when measured by a flow tester, a difference of the half melting temperature not greater than 10xc2x0 C. when two or more toners having different colors are used, a glass transition point not less than 50xc2x0 C. and a weight-average particle diameter not greater than 12 xcexcm (micrometers).
Further, the toner preferably includes a polyester resin or an epoxy resin as a binder resin.
These and other objects, features and advantages of the present invention will become apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.